Comment 15 for bug 1638338

I have encountered this bug today. You can reproduce it by launching ssh in Turkish locale environment:

LC_ALL=tr_TR.UTF8 ssh <email address hidden>

Ubuntu version is 16.10, and openssh-client version is 1:7.3p1-1. I guess the client converts parameters in config files to lowercase when parsing and gives error because both GSSAPIAuthentication and GSSAPIDelegateCredentials parameters has "I" character.

Turkish have two separate "i" character dotted and dotless. Per the Unicode standard, our lowercase "i" becomes "İ" (U+0130 "Latin Capital Letter I With Dot Above") when it moves to uppercase. Similarly, our uppercase "I" becomes "ı" (U+0131 "Latin Small Letter Dotless I") when it moves to lowercase.

For additional info, you can check out the links below:
http://www.moserware.com/2008/02/does-your-code-pass-turkey-test.html
https://blog.codinghorror.com/whats-wrong-with-turkey/
http://mattryall.net/blog/2009/02/the-infamous-turkish-locale-bug